The long range purpose of this project is to increase the understanding of the basic mechanisms of electrolyte transport in guinea pig cochlea under normal conditions and under the influence of physical and chemical agents. The flux of 42K, 22Na and 36Cl from the perilymph to endolymph was measured by perfusing the perilymphatic space with artificial perilymph containing these radioisotopes. The endolymph actively takes up 42K against the electrochemical gradient and extrudes 22Na. 36Chloride diffuses passively from the perilymph to endolymph. Ouabain and anoxia suppress the uptake of 42K and extrusion of 22Na. The concentration of -Cl in the endolymph was decreased and the uptake of 36Cl of the endolymph was also suppressed by anoxia. The effect of exposure to intense noise is under the initial stage of investigation. BIBLIOGRAPHIC REFERENCE: Konishi, T., Walsh, P.J. and Hamrick, P.E.: Permeability of cochlear partition to potassium and sodium ions. J. Acoust. Soc. Amer. 60: S79, 1977.